[tor-bugs] #8171 [Flashproxy]: Facilitator tells proxies how often to poll

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#8171: Facilitator tells proxies how often to poll
-------------------------+--------------------------------------------------
 Reporter:  dcf          |          Owner:  aallai
     Type:  enhancement  |         Status:  new   
 Priority:  normal       |      Milestone:        
Component:  Flashproxy   |        Version:        
 Keywords:               |         Parent:        
   Points:               |   Actualpoints:        
-------------------------+--------------------------------------------------
 Flash proxies have a built-in hard-coded polling interval (currently 10
 minutes). When we needed to change the polling interval, I pushed a new
 version of `flashproxy.js` (commits 49de7bf6 and 69d429db). They should
 rather get their polling interval from the facilitator. That is, in
 response to a polling request, the facilitator sends back
 {{{
 client=&check-back-in=600
 }}}
 meaning, no client now, try again in 10 minutes. Send `check-back-in` even
 if the response contains a client.

 The benefits of the facilitator controlling the polling interval are:
  * facilitator can dynamically change the interval to maintain a desired
 polling level
  * different intervals can be given to IPv4 and IPv6 proxies (we want IPv6
 to poll faster because there are fewer of them)
  * we want to rate-limit polling (#7823) and it means changing policy in
 just one place (the facilitator) and not having to change proxy code at
 the same time to match.

 The logic behind this needs to be in `facilitator`, not `facilitator.cgi`.
 In other words, `facilitator.cgi` sends to facilitator
 {{{
 GET FROM=1.2.3.4:10000
 }}}
 and `facilitator` sends back
 {{{
 NONE CHECK-BACK-IN="600"
 }}}
 or
 {{{
 OK CLIENT="9.9.9.9:9999" RELAY="123.123.123.123:9901" CHECK-BACK-IN="600"
 }}}

 Dynamic changing of the polling interval is not part of this ticket. This
 ticket is only to hardcode 10 minutes in the facilitator and to make
 proxies obey it.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8171>
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